Other methods:(assuming you didn't already try the above)
(dijichi2) if you get stuck and really want to just purge it from the system, try:rpm -e `rpm -qa |grep zimbra`rm -rf /opt/zimbradelete zimbra entries from /etc/sudoersdelete zimbra entries from root and zimbra crontabs

On Ubuntu servers dpkg may think that Zimbra is still installed. Check by running dpkg --list (-l)
or dpkg -q zimbra*
and see if zimbra items are still listed. You can remove them by running:dpkg --remove zimbra-apache zimbra-ldap zimbra-mta zimbra-spell zimbra-core zimbra-logger zimbra-snmp zimbra-store
or